Preparation of furfurylamines



Patented Oct. 10, 1939 UNITED STATES PATENT OFFICE Winans, Akron, Ohio No Drawing. Application April 14, 1936. Serial No. 74,342

Claims.

This invention relates to the catalytic synthesis of furfuryl secondary and tertiary amines. More particularly, it relates to a process for the catalytic synthesis of furfuryl-amines by the hydrogenation of reaction products of furfural and amines. It includes the products of the process. By the discoveries of this invention, furfuryl secondary and tertiary amines of high purity may be prepared quickly, efiiciently and in ex- 10 cellent yields. Of the starting materials, the furfural may be either the alpha or beta isomer. Since alpha furfural, however, is more commonly found in commerce, it will be understood that the use of alpha furfural is preferred in the practice of the invention. of the amine starting materials, any primary or secondary amine may be used. The pressures found preferable will in general range from 50 to 150 atmospheres, although much lower pressures, as low as 5 atmospheres, may be used in some instances. In such cases the time of reaction will be somewhat.

longer and it will be found desirable in most cases to use a pressure in the stated preferred range.

Higher pressures than 150 atmospheres may be as employed if the apparatus in which the process is carried out is sufliciently strong, although generally there will be no object in employing such higher pressures.

A superatmospheric temperature should also 80 be used but, where carefully purified furfural is used, it should preferably not be permitted to rise above about 110 C. for any great period of time during the reaction, for the reason that above about 110 C. the furane ring is reduced to the tetrahydro furane ring, thereby producing tetrahydro furfuryl amines rather than the furfuryl amines of the invention. The preferred range is from 50 to 110 C. although it will be understood that in some cases temperatures as low as 25 may be used. If the furfural is not carefully purified to remove sulphur compounds before 'use, temperatures of about 2550 C. higher than those stated may be necessary and will not cause reduction of the furane ring.

The furfural and the amine may be mixed just prior to hydrogenation or they may be first reacted and the product isolated, this product then being hydrogenated. It is generally preferable in the case of furfural-primary amines first to isolate the product, thereby separating the water formed which, if not eliminated or provided for, will cause the catalyst to cake in the subsequent hydrogenation step and thus reduce the efficiency of the process. If the furfural-primary amine product is not isolated prior to the hydrogenation Schiff base and the water formedare soluble.

In those cases where secondary amines are employed, their reaction products with furfural are usually so unstable that it is desirable to hydrogenate the mixture of amine and furfural directly, preferably in a water miscible solvent. It is,

of course, to be understood that with both primary and secondary amines either mixtures or 10 isolated reaction products with furfural may be used in the practice of the invention. Also, in any event where the reaction product is a solid at ordinary temperatures or where the amine in the mixture is a solid, it is preferable to em- 15 ploy a solvent, which as stated, should be miscible with water.

Although any of the ordinary hydrogenation catalysts is applicable for use in the invention, it has been found that the nickel catalyst pre- 20' pared by the treatment of a nickel alloy, such as nickel-aluminum, or nickel-silicon, withaqueous alkalis, as described in United States Patent 'No. 1,628,190 to Raney, is particularly suitable. Another nickel catalyst which may be employed with excellent results is the supported nickel catalyst described in Adkins application Serial No. 616,093, filed June 8, 1932, now matured into Patent No. 2,040,233, and prepared by mixing an aqueous solution of a nickel salt and a foram- 3o inous carrier, preferably acid-washed kleselguhr, and thereafter grinding the carrier-nickel salt mixture until it is of a cream-like consistency. Following this, a carbonate precipitant which reacts basic to litmus .paper, preferably an aque- 3'5 ous solution of an ammonium or alkali metal carbonate, such as ammonium carbonate, sodium carbonate or sodium bicarbonate, is added to the mixture, maintained during the addition of carbonate at a temperature of 70-80" C. After 40 washing and drying, the resulting precipitated nickel carbonate is reduced in a stream of hydrogen or other reducing gas for approximately -80 minutes at 425-475 C., the finished catalyst containing 15 2% nickel. Other catalyst 45 prepared in a similar manner may also be used, examples being those of copper and cobalt.

Platinum and other noble metal catalysts may be employed with very good results, but because of the lower cost of the base metal hydrogena- 50 tion catalysts, the latter will generally be found more desirable.

Nickel catalysts prepared by other methods, such as the following, may also be used in the practice of the invention: (1) the reduction of $51 nickel oxides, silicates, carbonates and. bicarbonates, either supported or unsupported, by hydrogen or other reducing agent: (2) the reduction of nickel oxides, silicates. carbonates and bicarbonates in admixture with salts of other metals of Group VIII or I of Mendelejefls Perlodic Table, the reduced salts acting as co-catalysts; (3) the reduction of nickel oxides, silicates, carbonates and bicarbonates mixed with promoters such as oxides of the metals of-Group 11, III, IV, V and VI of Mendelejefls Periodic Table; (4) anodic oxidation of nickel surfaces followed by reduction; (5) precipitation by more electropositive metals such as aluminum and zinc. The catalyst used should, of course, be active at a temperature below the decomposition temperature of the furfural-amine compound.

As illustrative of the invention, but not limitative thereof, the following examples are given:

Example 1 1.65 mols of fur-fural-n-butyl amine, a liquid boiling at 110-115 C. at 32 mm. pressure, were hydrogenated in the presence of about 10 grams of a Raney nickel catalyst prepared by the treatment of a nickel aluminum alloy with an aqueous alkali, as described in U. 8. Patent No. 1,628,190. Hydrogen was absorbed, the pressure ranging from 100 to 150 atmospheres. The time of reaction until sumcient hydrogen was absorbed to saturate the carbon to nitrogen double link was 3% hours, the temperature rising to a maximum of 110 C. during this period and being maintained at this figure for approximately two hours. The product, upon fractional distillation, gave a 75% yield of furfuryl-N-butyl amine, boiling point 92-l00 C. at .30 mm. pressure.

Example 2 1.4 mols of fur-fural-benzyl amine, a liquid boiling at 129-13? C. at 2 mm., and about 10 grams of a Raney nickel catalyst were placed in a copper liner and enclosed in a hydrogenation bomb. The mixture was submitted to agitation and hydrogen was then introduced to a pressure of 100 atmospheres in a bomb and the contents heated to 85 C. in a period of approximately minutes. The temperature was maintained at this figure for a period of approximately 70 minutes at which time the absorption of hydrogen was stopped and corresponded to the formation of furfuryl benzyl amine. Upon fractional distillation of the product, a 91% yield of furfuryl benzyl amine, boiling point 118-120 C. at 2 mm. pressure, was obtained. The benzoyl derivative of this product melted at 7172 C. and was found to contain an average nitrogen analysis of 4.81% as compared with the calculated nitrogen analysis for the benzoyl derivative of furfuryl benzyl amine of 4.83%.

Example 3 0.27 mol of furfural-p-amino phenol, a solid melting at 187-1875 C., was dissolved in ethanol and in the presence oi about 5 grams of a Raney nickel catalyst was subjected to a hydrogen pressure of approximately 100-150 atmospheres for a period of one hour at a maximum temperature of 75 C. The reduction of the carbon to nitrogen double linkage was practically quantitative, a 99% yield 01' furfuryl-p-amino phenol, melting point 108-110 C., being obtained. The product upon analysis was found to contain 7.35% nitrogen as compared with the theoretical nitrogen content of furfuryl-p-amino phenol of 7.41%.

Example 4 Upon. the hydrogenation of an ethanol solution of 0.21 mol of di furfural benzidlne, a solid melting at 2l2-213 C., in the presence of about 5 grams of a Raney nickel catalyst for a period of 3 hours at a maximum temperature of 75 C. and a pressure ranging from 100150 atmospheres, a 79% yield of N-N'-difurfuryl benzidine, melting point 155.5-156 C. was obtained. An analysis of the product gave 8.35% nitrogen as compared with the theoretical nitrogen content for di furfuryl benzidine of 8.13%.

Example 5 An ethyl alcohol solution of 0.19 mol of di Iurfural p-phenylene diamine, a solid melting at 164-165 C., and about 5 grams of a Raney nickel catalyst were subjected to a hydrogen pressure of 100-150 atmospheres for a period of one hour at a maximum temperature of 75 C. Upon separation of the product, a 90% yield of N-N'-di furfuryl-p-phenylene diamine, melting point 75-77 C., was obtained. This product was found to contain 10.35% nitrogen as compared with the theoretical nitrogen content for di furfuryl-p-phenylene diamine of 10.45%.

Example 6 CHI-CH: HC--OH Distillation of the filtered reaction mixture gave the following fractions:

(1) Up to 90 C. mm.-Alcohol solvent, etc.

.(2) From 90 to 120 C. 30 mm. (mostly at 110-120 C. 30 mm.)68.5 grams of N-furiuryl piperidine.

(3) Above 120 C. 30 mm.Black viscous tar.

Fraction 2 was identified as N-furfuryl piperidine by its unreactivity with nitrous acid (characteristic of tertiary amines), and by its formation with picric acid of a crystalline salt melting at 107-108 C. Also, an analysis of this salt for picric acid gave 58.2% as compared with the theoretical figure of 58.1% for the picric acid salt of N-furfuryl piperidine. The rather low yield of N-furfuryl piperidine may be ascribed in part at least to the crude furfural employed.

From these illustrative examples it is apparent that the invention provides a novel class of compounds as well as an efiicient process for preparing them. In each of the examples the furfural employed was freshly distilled and of a high degree of purity. While Example 1 required a longer time and a higher temperature than is usually necessary in the practice of the invention, this was caused by chloride impurities in the butylamine. which reduced the activity of the catalyst. While the examples have described the preparation principally of iuriuryl secondary amines, which are the preferred class of the compounds of the invention, it will be understood that tertiary amines may be prepared by the same process merely by substituting a secondary amine for the primary amine starting material. Illustrative of such tertiary amines are the furiuryl amines oi morpholine, dicyclohexyl amine, dibenzyl amine, N-ethyl cyclohexylamine, dimethyl amine, N-butyl tetrahydrofuriurylamine, ethyl aniline diamyl amine, dibutyl amine, di- (beta phenyl ethyl) amine, diphenyl amine, symdibutyl ethylene diamine, N -isopropy1 beta naphthylamine, N-cyclohexyl aniline, diethyl amine, ditetra hydro Iurfuryl amine, N-ethyl decahydro naphthylamine, etc. Other furiuryl secondary amines of the invention are those prepared by treating iuriural in the process of the invention with such amines as ethyl amine, aniline, furfuryl amine, para phenetidine, beta phenethyl amine, ortho toluidine, the alpha and beta primary naphthylamines, tetrahydro furfuryl amine, cyclohexyl amine, heptyl amine, the AR- and AC- tetrahydro primary naphthylamines, 0- amino phenol, xylidine, tolidine, ethanolamine, amino pyridine, methyl amine, ethylene diamine, propylamine, isopropylamine, n-amylamine, isoamylamine, sec. amylamine and the amylenefliamines. Other iurfuryl secondary amines are those of hexahydro oand p-anisidine, hexahydro oand p-toluidine, hexahydro oand p-phenetidlne, and of other alkoxy substituted alicyclic amines. Still others are the furiuryl derivatives of the decahydro naphthylamines, alpha and beta, of the alicyclic amino acids and esters thereof, such as\oi' hexahydro anthranilic acid and of its esters. Other iurfuryl amines are those pre- 'pared by reducing the products of iuriural with the nitro anilines, with the nitro toluidines, with the cumidines, with the chlor phenylamines and with the hydroxy-, alkyl-, carboxylicand nitronaphthylamines.

It is readily seen that by this invention a very efllcient method oi preparing amines by hydrogenation is provided. The reaction may be carried out in the liquid phase under pressure, thereby permitting the use of more compact, eiiicient and simplified apparatus. It also permits greater ease in accuracy in the manipulation of the ingredients and the final products. By the use of pressures the reactions are driven to completion quickly and efliciently, the necessity for vaporizing the ingredients is overcome and syntheses not heretofore capable of being accomplished are made possible. Also, a novel class of amines is provided. They may be used in the vulcanization of rubber and as intermediates in the prepara-. tion oi rubber vulcanization accelerators.

This application is, in part, a continuation of application Serial No. 619,732, filed June 28, 1932,

of patentable novelty inherent in the invention.

What we claim is:

l. The process for preparing iuriuryl secondv ary and tertiary amines which comprises hydrogenating under superatmospheric pressure, at a superatmospheric temperature or not above about 110 0., in the liquid phase and in the presence of a base metal hydrogenation catalyst, a reaction product of furiural and an amine containing the group NH Bi wherein at least one of the'R groups is hydrocarbon.

2. The process for preparing furfuryl secondary and tertiary amines which comprises hydrogenating in a closed vessel under superatmospheric pressure, at a superatmospheric temperature of not above about 110 C., in the liquid phase and in the presence of a nickel catalyst, a mixture of furiural and a primary amine.

3. The process for preparing furfuryl secondary and tertiary amines which comprises hydrogenating in a closed vessel under superatmospheric pressure, at a superatmospheric temperature of not above about 110 C., in the liquid phase and in the presence of a nickel catalyst, a mixture of furiural and a secondary amine.

4. The process for preparing iurfuryl secondary and tertiary amines which comprises hydrogenating in a closed vessel under superatmospheric pressure, at a superatmospheric temperature of from about C. to about 110 C., in the liquid phase and in the presence of a base metal hydrogenation catalyst, a mixture of furfural and a saturated amine containing at least one hydrogen atom attached to an amino nitrogen atom.

5. The process of preparing N-cyclohexyl furiuryl amine which comprises hydrogenating furiural and cyclohexyl amine at a temperature of from about 50 C. to about 110 'C., under a superatmospheric pressure, and in the presence of a nickel catalyst.

6. The-process oi, preparing furiuryl p-amino phenol which comprises hydrogenating furfural and peamino phenol at a temperature of from about 50 C. to about 110 C., under a superatmospheric pressure, and in, the presence of a nickel catalyst.

'7. The process of preparing N-iuriuryl n-butyl amine [.which comprises hydrogenating iurfural and n-butyl amine at a temperature of from about C. to about 110 C., under a superatmospheric pressure, and in the presence of a nickel hydrogenation catalyst.

8. The process for preparing furfuryl secondary and tertiary amines which comprises hydrozenating under superatmospherlc pressure, at a superatmospheric temperature of not above about 110 C., in the liquid phase and in the presence of a hydrogenation catalyst selected from the group consisting oi. nickel and cobalt, turtural and an amine containing at least one hydrogen atom attached to an amino nitrogen atom.

9. The process for preparing iuriuryl secondary and tertiary amines which comprises hydrogenating in combination iuriural and an amine containing at least one hydrogen atom attached to an amino nitrogen atom, in the liquid phase, in the presence of a hydrogenation catalyst and under superatmospheric conditions of temperature and pressure inducing absorption of hydroge at the linkage of the iuriural with the amine bu not causing reduction of the iurane ring.

1 N-iuriuryl N-(p-hydroxy phenyl) amine.

HOMER. ADKINS. CHARLES 1!. WINANS. 

